The proposal is concerned with research on visual development in infant pigtail macaque monkeys (Macaca nemestrina). Four specfic kinds of studies are proposed: 1. Normal development of spatial vision (visual acuity and contrast sensitivity functions). Both operant and preferential looking techniques will be employed for behavioral testing of infants of various ages. 2. The effects of two kinds of visual deprivation. Some infants will be reared with an externally applied optical astigmatism, while others will be deprived of specific spatial frequency bands. These deprivation conditions will sometimes be introduced or alleviated for short periods of time during development, to determine the time periods (critical periods) during which specific deprivation interferes with the normal development of spatial vision, or during which normal visual exposure can prevent the harmful effects of visual deprivation. 3. The development of optical quality in the infant monkey eye. Direct measurements will be made of optical quality. A combination of optical and behavioral studies will be used with the goal of separating the visual limitations of primate infants into optical and neural components. 4. Neuroanatomical studies. Golgi studies will be conducted on tangential sections taken from the visual cortices of these monkeys in order to look for neural correlates of spatial vision. The long-range objective of the research is to use the infant monkey as an animal model for the development of human vision, both when the developmental process proceeds normally and when it is disrupted in specific ways.